JPH06213081A - EGR device of engine - Google Patents

Abstract

PURPOSE:To reduce the NOx in realizing the stratified combustion of both mixed and unmixed flows of exhaust gas by forming an exhaust gas supply port in a partial intake passage alone, and connecting this supply port to an exhaust through a course followed, in an exhaust gas recirculation system which recirculates the exhaust gas to a combustion chamber of an engine equipped with plural lines of an intake passage. CONSTITUTION:In a driving area where an intake air quantity is little, an intake control valve 18 is turned to the full-close position by a control unit 27, and a bottom wall side of each branch passage 7b is throttled down. In succession, intake air partially flows to a top wall side, producing a tumble, and combustion is stabilized. At this time, an exhaust gas feed pipe 25 is opened by the control unit 27 via an EGR control valve 26, while the exhaust gas is drawn into the branch passage 7b from the feed pipe 25 and a supply passage 23 with the open of an intake valve 9, making this exhaust gas mix the intake air flowing into the top wall side. With this constitution, a flow velocity of the intake air is heightened, thereby producing the tumble with certainty. In addition, a mixed flow of the exhaust gas is fed to the vicinity of a spark plug, and an initial combustion temperature is lowered to some extent and thereby a harmful ingredient in the exhaust gas is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device for an engine which mixes exhaust gas with intake air and recirculates it into a combustion chamber, and particularly when a plurality of intake passages are provided, an exhaust gas mixture flow and an exhaust gas The present invention relates to improvement of an exhaust gas supply position that enables stratified supply of a mixed flow.

[0002]

2. Description of the Related Art For example, in an engine for an automobile, an EGR device has been conventionally used which lowers a combustion temperature to reduce a generation amount of NOx by recirculating a part of exhaust gas together with intake air into a combustion chamber. Has been adopted. In this type of EGR device, a part of exhaust gas is recirculated to a surge tank common to each cylinder provided at an upstream end of an intake manifold, and a mixed flow of this exhaust gas, intake air, and fuel is introduced into a combustion chamber. It is generally supplied.

[0003]

In the above-mentioned conventional apparatus, the exhaust gas is evenly mixed with the intake air and supplied to the combustion chamber. As a result, there is a problem that a relatively large amount of exhaust gas needs to be supplied and HC (hydrocarbon) tends to increase in order to reduce NOx, or combustion tends to become unstable particularly in lean air-fuel ratio combustion. There is such a problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and supplies the exhaust gas mixed flow and the exhaust gas non-mixed flow in a layered manner to obtain a high NOx reduction effect with a small amount of exhaust gas, for example. Alternatively, the engine EGR that can stably perform lean air-fuel ratio combustion even if a large amount of exhaust gas is supplied
The purpose is to provide a device.

[0005]

According to a first aspect of the present invention, in an EGR device for recirculating exhaust gas into a combustion chamber of an engine having a plurality of intake passages, an exhaust gas supply port is provided only in a part of the intake passages. Is formed, and the exhaust gas supply port and the exhaust device are connected by a passage.

Further, the invention of claim 2 is characterized in that the exhaust gas supply port is formed so that the mixed flow of exhaust gas flows toward the ignition plug.
It is characterized in that the exhaust gas supply port is formed only in the intake passage connected to the intake valve opening that opens so that the intake flow flows away from the ignition plug.

Further, the invention of claim 4 is characterized in that an intake control valve for variably controlling the passage area of the intake passage is provided, and the exhaust gas supply port is formed on the downstream side of the intake control valve.

[0008]

According to the engine EGR device of the present invention,
Since the exhaust gas supply port was formed only in some intake passages,
The exhaust gas mixed flow and the exhaust gas non-mixed flow are layered and supplied to the combustion chamber, so that stratified combustion can be realized.

According to the second aspect of the invention, the exhaust gas mixed flow is supplied in the vicinity of the spark plug, so that the temperature of the initial combustion started around the spark plug can be lowered, and as a result, a large amount of NOx is reduced by a small amount of exhaust gas. The effect is obtained and H
C does not increase.

In the third aspect of the present invention, the intake passage that is not directed to the spark plug is selected as the part of the intake passage. Therefore, the air-fuel mixture containing no exhaust gas is supplied in the vicinity of the spark plug, so that the exhaust gas is exhausted. By supplying a large amount of NOx, the combustion stability can be secured while increasing the NOx reduction effect.

Further, according to the invention of claim 4, since the intake control valve for narrowing down the bottom wall side of the intake passage is provided at the time of the low intake air amount, the intake air is biased toward the top wall side of the intake passage at the time of the low intake air amount, A vortex (tumble) can be generated by flowing into the cylinder with directionality.

In this case, since the exhaust gas is supplied to the downstream side of the intake control valve, the intake flow velocity is increased by the amount of the exhaust gas and the directionality of the intake flow is further strengthened, or the intake control is performed. The generation of vortices on the downstream side of the valve can be suppressed, so that tumble is generated more reliably.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 3 are views for explaining an EGR device for an engine according to a first embodiment of the present invention as claimed in claims 1, 2 and 4, FIG. 1 is a schematic configuration diagram of the engine of the present embodiment, and FIG. FIG. 3 is a sectional side view showing the vicinity of the exhaust gas supply port.
FIG. 4 is a cross-sectional plan view showing the vicinity of an exhaust gas supply port.

In the figure, reference numeral 1 is a water-cooled 4-cycle in-line 4-cylinder 4-valve engine equipped with the apparatus of this embodiment, which is a crankcase integrated type (not shown) in which a cylinder block 2 and a cylinder head 3 are laminated. And a head cover 4 is attached to the cylinder head 3.

Cylinder bore 2 of the cylinder block 2
A piston 5 is slidably inserted in a, and the piston 5 is connected to a crankshaft (not shown) by a connecting rod 6. Further, four sets of combustion recesses 3a which form a combustion chamber with the upper surface of the piston 5 are provided on the block-side mating surface of the cylinder head 3. Two intake valve openings 7a, 7a and two exhaust valve openings 8a, 8a are provided in each combustion recess 3a.
Are formed and are led to the outer wall of the cylinder head through a bifurcated intake passage 7 and exhaust passage 8, respectively.

The intake valve opening 7a and the exhaust valve opening 8a can be opened and closed by an intake valve 9 and an exhaust valve 10, respectively.
The intake valves 9 and exhaust valves 10 are biased in the closing direction by valve springs, and are driven in the opening direction by intake and exhaust cam shafts 13 and 14 via lifters.

A surge tank 16 is connected through an intake manifold 15 to each external connection opening 7b formed in the cylinder outer wall of each intake passage 7, and the tank 16 is connected to the surge tank 16.
A throttle valve 16a is provided in the air introduction portion of the.
A fuel injection valve 17 is arranged on the top wall side of each branch of the intake manifold 15.

When viewed in the cam axis direction (see FIG. 2), the intake passage 7 is bent toward the rear wall of the cylinder head immediately upstream of the intake valve opening 7a and extends substantially straight. When viewed in the cylinder axis direction (see FIG. 3), the intake passage 7 has a structure in which two branch passages 7c and 7c are joined together at the external connection opening 7b.

A valve hole 7e is linearly formed in the intake passage 7 so as to penetrate the left and right side walls and the central partition wall 7d of each branch passage 7c in the cam axis direction. The valve hole 7e has a diameter substantially the same as the height of each branch passage 7c, and its center line is located slightly above the bottom wall surface of each branch passage 7c. Therefore, a recess 7e 'is formed in this bottom wall.

An intake control valve 18 for changing the passage area of each branch passage 7c is inserted through the valve hole 7e,
It is rotatably supported. The intake control valve 18 has a structure in which a valve portion 18a is formed by cutting a circular rod body, and the valve portion 18a is formed in a shape that can be flush with the inner surface of each branch passage 7c. . The intake control valve 18 has a fully open position in which the valve portion 18a is recessed into the recess 7e 'of the bottom wall so as to be flush with the inner surface of the passage, and a fully closed position in which the valve portion 18a stands upright and narrows the bottom wall side. It is possible to rotate between.

The intake control valve 18 of each branch passage 7c is also provided.
A rectifying plate 24 that rectifies the intake air so as to flow along the ceiling wall is disposed between the intake valve opening 7a and the intake valve opening 7a. The upstream end of the current plate 24 is located near the upper edge of the valve portion 18a located at the fully closed position, the downstream end is located closer to the center of the combustion chamber than the intake valve 9, and constitutes the intake valve opening 7a. It is fixed to the valve seat. Reference numeral 24a is an intake valve insertion hole, and a slight gap is provided between the insertion hole 24a and the intake valve shaft and between the left and right edges of the straightening plate 24 and the inner surface of the intake passage.

An exhaust manifold 20 of an exhaust device 19 is connected to the external connection opening of the exhaust passage 8.
A catalyst 21 is arranged at the confluence of the manifold 20. Reference numeral 22 is an O ₂ sensor for detecting the oxygen concentration.

The intake valve 9 of the cylinder head 3,
An exhaust gas supply passage 23 is bored in the camshaft direction between the exhaust valves 10. The exhaust gas supply passage 23 is located at the downstream end of each branch passage 7c, that is, above the intake valve opening 7a. In addition, in the exhaust gas supply passage 23, one injection hole (exhaust gas supply port) 23a is provided for each cylinder.
The injection holes 23a are directed toward the downstream edge of the straightening vane 24a on the right side (lower side in FIG. 2) of each cylinder and near the center edge of the combustion chamber.

The external connection port of the exhaust gas supply passage 23 is connected to the exhaust manifold 20 by an exhaust gas supply pipe 25.
Is connected to the exhaust gas outlet 20a formed in each of the cylinder branch portions. An EGR control valve 26 that opens and closes the exhaust gas supply pipe 25 is provided in the middle of the exhaust gas supply pipe 25.

The engine 1 of this embodiment has a control unit 27. Signals indicating various engine operating states such as a throttle valve opening signal a, an intake air amount signal b, a cam angle signal c, a water temperature signal d, and an oxygen concentration signal e are input to the control unit 27, and based on these signals. A control signal A for adjusting the opening / closing timing, opening time, etc. of the EGR control valve 26 is output to the EGR control valve 26, and a fuel injection valve control signal, an intake control valve control signal, etc. are output.

Next, the function and effect of this embodiment will be described. In the engine of this embodiment, the intake control valve 18 is controlled by the control signal from the control unit 27 in the operating range where the intake air amount is small, such as when the engine is operating at low load and low speed.
Rotating to the fully closed position shown in FIG. 2, each valve portion 18a narrows down the bottom wall side of each branch passage 7c by about 50 to 70%. As a result, intake air flows unevenly toward the top wall and flows vertically into the cylinder from the vicinity of the center of the combustion chamber, resulting in tumble and stable combustion at low intake air amounts. Further, the above-mentioned uneven flow is further rectified by the straightening plate 24 into a flow along the ceiling wall,
As a result, the tumble is generated more reliably, and the combustion is performed when it is more stable.

In this case, the control unit 2
The EGR control valve 26 opens the exhaust gas supply pipe 25 according to the control signal A from 7 and the exhaust gas is supplied from the supply pipe 25, the supply passage 23, and the injection hole 23a into the branch passage 7c with the opening of the intake valve 9. Is sucked in, is mixed with the intake air flowing on the ceiling wall side, and is introduced into the cylinder. The exhaust gas acts to increase the flow velocity of the intake air and more reliably generate the tumble.

The exhaust gas mixed flow is supplied near the center of the combustion chamber, that is, in the vicinity of the spark plug 28. As a result, the temperature of the initial combustion that occurs near the spark plug can be lowered, NOx can be reduced with a small amount of exhaust gas, and the amount of HC generated can be suppressed.

FIGS. 4 and 5 show a second embodiment according to the invention of claims 1, 2 and 4, in which the same reference numerals as those in FIGS. 1 to 3 designate the same or corresponding parts. In the second embodiment, the exhaust gas supply passage 33 is arranged below the intake passage 7 so as to extend in the cam axis direction. Further, the injection hole 33a is arranged below the valve hole 7e so as to extend in the direction perpendicular to the cam axis, and is opened so as to be located near the combustion chamber in the vicinity of the intake valve opening 7a of the right branch passage 7c. There is.

In this embodiment, the exhaust gas is supplied from the injection hole 33a toward the center of the combustion chamber in the direction perpendicular to the cam axis. Therefore, the exhaust gas mixed flow is supplied in the vicinity of the ignition plug 28, and the initial combustion temperature is lowered to reduce NOx as in the first embodiment.
A reduction effect can be obtained.

Further, in this embodiment, the exhaust gas suppresses the generation of vortices on the downstream side of the intake control valve, thereby making the generation of tumble more reliable.

6 to 8 show a third embodiment according to the invention of claims 1 and 2, wherein the same reference numerals as those in FIGS. 1 to 7 designate the same or corresponding parts. In this embodiment, five intake valves are used.
It is an example of a valve engine.

Left and right side intake valve openings 7a, 7a and a center intake valve opening 7f are formed in each combustion recess 3a so as to surround the ignition plug 28, and the respective openings are left and right side intake passages 7c, 7c. The center intake passage 7g is led out to the external connection opening 7b. Further, a joint 17a is connected to the external connection opening 7b.
a is a partition wall 1 that extends the partition wall 7d of each intake passage.
7b is formed.

A fuel injection valve 17 is arranged in the center of the top wall of the joint 17a in the width direction, and the fuel injection valve 17 is mainly configured to inject fuel into the center intake passage 7g. An exhaust gas supply port 17c is opened in the center of the bottom wall of the joint 17 in the width direction, and the supply port 17c is configured to supply exhaust gas to the center intake passage 7g. A downstream end of an exhaust gas supply pipe 25 is connected to the exhaust gas supply port 17c, and an upstream end of the supply pipe 25 is connected to an exhaust gas outlet port 8b which is opened on a top wall of the merging portion of the exhaust passage 8. ing.

In this embodiment, since the exhaust gas is supplied toward the center intake passage 7g directed to the spark plug 28, the exhaust gas mixed flow is distributed around the spark plug 28 in the first and second embodiments. It is more reliably supplied, and the initial combustion temperature can be lowered with a smaller amount of exhaust gas to reduce NOx.

9 to 11 are views for explaining a fourth embodiment according to the invention of claims 1 and 3, and in FIG.
8 to 8 indicate the same or corresponding parts. In this embodiment, an injection hole (exhaust gas supply port) 33a is opened in the bottom wall of the side intake passage 7c, and the supply port 33a is connected via the exhaust gas passage 33, the branch pipe 25a, and the exhaust gas supply pipe 25. It is connected to the exhaust gas outlet 20a of the exhaust manifold 20. In addition, in this embodiment, each of the branch pipes 25
The EGR control valve 26 is provided in a for each cylinder.

In this embodiment, fuel is injected from the fuel injection valve 17 toward the center intake passage 7g, and exhaust gas is supplied to the side intake passage 7g. Therefore, in the present embodiment, a mixture of air and fuel containing no exhaust gas (see reference numeral a in FIG. 10) is supplied around the spark plug 28 near the center of the combustion chamber, and air is supplied to the periphery of the combustion chamber. And a mixed flow of exhaust gas (see reference numeral b in FIG. 10) are supplied.

As described above, in this embodiment, the exhaust gas non-mixed flow is supplied around the spark plug 28, and the exhaust gas mixed flow is supplied around the spark plug 28 in a layered manner to perform stratified combustion. Therefore, in this embodiment, even if the exhaust gas amount is increased in the lean air-fuel ratio operation, the combustion can be stably performed, and the NOx emission amount can be reduced.

[0039]

As described above, the E of the engine according to the present invention is
According to the GR device, since the exhaust gas is supplied only to a part of the intake passage, the stratified charge combustion can be realized.
In the invention of claim 1, an exhaust gas mixed flow can be supplied around the spark plug, the initial combustion temperature is lowered, and high NO
x reduction effect can be obtained, and in the invention of claim 3, since exhaust gas is not supplied around the spark plug, there is an effect that combustion can be stabilized even if a large amount of exhaust gas is introduced. In the invention of claim 4, since the exhaust gas is supplied to the downstream side of the intake control valve, there is an effect that the tumble can be strengthened.

[Brief description of drawings]

FIG. 1 is a cross-sectional side view of an engine including an intake control device according to a first embodiment of the present invention.

FIG. 2 is a sectional side view showing an exhaust gas supply port of the engine of the first embodiment.

FIG. 3 is a sectional plan view showing an exhaust gas supply port of the engine of the first embodiment.

FIG. 4 is a sectional side view showing an exhaust gas supply port of a second embodiment according to claims 1, 2, and 4.

FIG. 5 is a cross-sectional plan view showing an exhaust gas supply port of the second embodiment device.

FIG. 6 is a sectional side view showing an exhaust gas supply port of a third embodiment according to claims 1 and 2.

FIG. 7 is a sectional side view showing an exhaust gas outlet of the third embodiment.

FIG. 8 is a sectional plan view showing an exhaust gas supply port of the third embodiment.

FIG. 9 is a sectional plan view of a third embodiment according to claims 1 and 4.

FIG. 10 is a schematic diagram for explaining the operation of the third embodiment.

FIG. 11 is a schematic configuration diagram of the third embodiment.

[Explanation of symbols]

 1 Engine 3a Combustion concave part (combustion chamber) 7a, 7f Intake valve opening 7c, 7g Intake passage 18 Intake control valve 19 Exhaust device 23a, 33a (Injection hole) Exhaust gas supply port 25 Exhaust gas supply pipe (passage) 26 EGR control valve (Open / close valve) 28 Spark plug

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location F02B 31/00 L 7541-3G F02M 35/10 311 E 9247-3G F02P 13/00 303 Z

Claims (4)

[Claims] 1. An EGR device for recirculating exhaust gas to a combustion chamber of an engine having a plurality of intake passages, wherein an exhaust gas supply port is formed only in the part of the intake passages, and the exhaust gas supply port and the exhaust gas are exhausted. An EGR device for an engine, characterized in that it is connected to the device through a passage. 2. The EGR device for an engine according to claim 1, wherein the exhaust gas supply port is formed so that an exhaust gas mixed flow flows toward a spark plug. 3. The engine according to claim 1, wherein the exhaust gas supply port is formed only in an intake passage that is connected to an intake valve opening that opens so that the intake flow flows away from the ignition plug. EGR device. 4. The intake control valve according to claim 1, wherein an intake control valve for variably controlling a passage area of the intake passage is provided, and the exhaust gas supply port is formed on a downstream side of the intake control valve. EGR device for engine.